Related Experiment Video
Updated: Jul 16, 2026

Collecting Hair Samples for Hair Cortisol Analysis in African Americans
Published on: June 10, 2018
Relaxing/straightening of Afro-ethnic hair: historical overview
Tania Cristina de Sá Dias1, André Rolim Baby, Telma Mary Kaneko
1Department of Pharmacy, School of Pharmaceutical Sciences, University of São Paulo, Conjunto das Químicas, Cidade Universitária, São Paulo, SP, Brazil.
Abstract:
Afro-ethnic hair, when compared with naturally straight hair, presents some important variations such as differences in diameter in many points of the thread, ellipsoidal threads, and low trend of hydrating the scalp thus turning the hair drier, because the natural sebum distribution is irregular along the thread. This kind of hair may be straightened through both chemical and thermal methods. Straightening is a chemical process by which excessively curly hair is straightened in an irreversible way. Generally, the products used are formulated in a cosmetic emulsion with high pH. In this review, we present the historical development of hair straightening or relaxing through the evolution of the product categories.
Related Concept Videos
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Atomic Force Microscopy
The AFM Probe
The probe is regarded as the heart of any AFM setup and comprises the...
Accessory Structures of the Skin: Hair Growth and Types
Atomic Nuclei: Types of Nuclear Relaxation
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
Transformation of Plane Stress
Three-Dimensional Analysis of Strain

